This invention relates to antimicrobial, biocompatible products wherein said antimicrobial property is non-leaching and not dependent on antibiotic drugs. Applicants"" products include polymerizable substrates and quaternary salts which adhere to the substrates through an IPN. Applicants"" invention also includes other products wherein the impregnation or adherence of the quaternary salts is achieved by processes other than the formation of an IPN. The products encompassed by Applicants"" invention include catheters, coatings and food processing belts.
Quaternary ammonium salts have the general formula of:
[(CH3)4N]+Xxe2x88x92xe2x80x83xe2x80x83(1)
where X is a halogen such as iodine, chlorine or bromine. A variety of quaternary ammonium compounds are available and widely used as disinfectants and biocides and to treat items that may undesirably support microbial growth. For example, quaternary ammonium salts are used to treat carpeting, walls, various commercial products such as sponges and fabrics, and even water. They are also used to rehabilitate xe2x80x9csick buildings,xe2x80x9d particularly after floods and water leaks, and reduce odors caused by mildew, fungus and bacterial growth in damp basement areas.
Most quaternary ammonium salts commercially available are generally pre-packaged in water or alcohol solutions of approximately 2-3% or less quaternary salt concentration. They are applied to substrates such as carpets, walls, floors, to kill the bacteria. The method of application often relies on delivering the quaternary ammonium salt in a fine spray. When treating fabrics, sponges, bedding, and similar products, the concentration of the quaternary ammonium salts generally can be much lower, e.g., less than 1%.
Despite knowledge of the common usage of quaternary ammonium salts for imparting antimicrobial properties, products have not been known that include such salts and are biocompatible.
Applicants"" products use quaternary ammonium salts of the general formula of: 
wherein R1 and R2 are methyl (CH3) groups; R3 is an octadecyl (CH3(CH2)17) group; and R4, R5 and R6 are methoxy (OCH3) groups. Applicants"" products are created using a method that is applied either during or after manufacture, such that the resulting products have long-lasting, non-leaching, biocidal properties on the surface and are not toxic to the host organism. The treatment involves converting the methoxy groups to OH groups though hydrolysis and then polymerizing through condensation of the OH groups to form siloxane bonds and water
More specifically, because catheter infections are the leading cause of hospital or long-term care infections, numerous attempts have been made to create a catheter that is antimicrobial. Most antimicrobial catheters rely on the impregnation of antibiotics to achieve a catheter that is resistant to bacterial infection. Unfortunately, this use of antibiotics results in increased resistance to antibiotics, a significant problem for immuno-compromised patients. It also leads to the subsequent long-term inefficacy of such catheters.
Further, some antimicrobial catheters use a coating treatment to provide a vehicle for entrapping drugs onto the catheter surface but permit subsequent diffusion into the biological environment. Many such treatments rely upon a polyurethane in a solvent to entrap antibiotic pharmaceutical agents.
Similarly, the food processing industry has had a long felt need for a food conveyor belt that facilitates the transfer of food products without bacterial infection. The creation of such belts has been complicated by the need to achieve such protection without antibiotics and wherein the antimicrobial property endures despite the abrasion inflicted on such food processing belts.
Thus, despite numerous and concerted efforts, cost-efficient products have not been devised that have non-leaching, biocompatible, antimicrobial surfaces. In particular, despite the long felt need for such products in the food processing and catheter industries, until Applicants"" invention no such products existed.
Interpenetrating polymer networks (IPNs) are well known in the art. They are prepared in a variety of ways and the technical literature is replete with the technology for the manufacture of such IPNs. The most common ways to create IPNs are (1) by blending two or more polymers in an internal mixer using temperature, mixing time and torque to obtain a blended or grafted IPN, and (2) by xe2x80x9cswelling,xe2x80x9d i.e., expanding, a higher polymer with a monomer or a solution of a monomer and polymerizing the monomer to a polymer in situ.
In this latter case, when monomer (A) is polymerized to form a polymer (A) in a host or substrate polymer (B), such as silicone or polyurethane elastomer, a high degree of permanence can be established for polymer A. That is, polymer A can only be removed to a limited degree when the IPN is extracted by an organic solvent or water. Therefore, such an IPN has long term stability.
However, until now, IPNs of polymerized quaternary ammonium salt monomers have not been used to impregnate the surfaces of medical devices and supplies to impart antimicrobial properties to such devices and supplies. Applicants accomplish this in such a manner that does not compromise their biocompatibility.
It is an object of this invention to provide products having an interpenetrating network on the surface that is biocompatible and antimicrobial.
It is a further object of the invention to provide consumer products having a biocompatible and antimicrobial surface.
It is an object of the invention to provide products that are antimicrobial and may be implanted in or used on living organisms.
It is a further object of the invention to provide an antimicrobial catheter that is not dependent on antibiotic drugs for antimicrobial activity.
It is an object of this invention to provide a polymeric coating having antimicrobial properties that can be applied to various medical device and supply surfaces.
It is also an object of this invention to provide a durable food processing surface having antimicrobial properties.
Other objects of the invention will be obvious upon reading the following specification and claims.
Applicants"" products have a surface impregnated with quaternary salts that have antimicrobial characteristics and are polymerizable. Applicants"" products have an IPN formed by a quaternary salt in or on the underlying substrate material. In one embodiment of Applicants"" invention, the quaternary salt is polymerized after it has penetrated the surface of the host polymer, i.e., the polymer on the surface of the product to be treated. The depth of the penetration of the quaternary salt in the host polymer is controlled by the period of time that the polymeric substrate is exposed to the solution containing the quaternary salt, and solvent power, i.e., how much of the solvent is adsorbed by the subject device or product during the exposure period. The solvent power is reflected by the weight gain of the subject device or product during the exposure period.
After the quaternary salt monomer has been absorbed by the host polymer, the quaternary salt is polymerized to form an interpenetrating network polymer (IPN). Such polymerization preferably is achieved by using 0.1 N NaOH, 0.1 N HCl, heat or a combination thereof The presence of the interpenetrating polymer (i.e., the active quaternary ammonium group) has been substantiated by a dye test using bromophenol blue. The longevity or permanence of the quaternary ammonium group has been demonstrated by dye testing the treated material after repeatedly challenging the treated host substrate with multiple hot (e.g., 140xc2x0 F.) water rinses, aging treated samples with forced air or in a microwave oven, and subjecting the treated sample to repeated autoclave cycles (270xc2x0 F. for 30 minutes).
As the following non-limiting examples show, the IPNs of silicone and polyurethane rubber, including silicone and polyurethane rubber catheters of Applicants"" invention, have been shown to possess the ability to kill bacteria, fungi and molds.
In other embodiments of Applicants"" invention, a non-leaching antimicrobial IPN is created within the cavities and pores of the material to be treated. This embodiment does not require that the material to be treated be swelled. Rather, the quaternary salt monomer/solvent are absorbed into the pores, the solvent is evaporated and the monomer is polymerized within and through the pores of the substrate. In this manner the polymerized quaternary salt is xe2x80x9canchoredxe2x80x9d to the substrate through a physical interaction or blending. The level of quaternary salt polymer should be less than about 5% by weight on the substrate to minimize the decrease of air flow through the polymer substrate.
Another embodiment of Applicants"" invention is a polymeric coating that can be applied to a variety of non-polymeric surfaces.
One embodiment of Applicants involves products wherein a host polymer is swollen with a solvent solution of quaternary ammonium salt. Preferably, the solvent is selected based on its ability to swell rapidly the host polymer the desirable amount without significantly disrupting the integrity of the underlying host substrate. Even more preferably, the appropriate and necessary amount of swelling of the host substrate, e.g., as reflected by an approximately 20 to 50 percent weight gain of the solvent and quaternary salt, occurs within 10 minutes or less after exposure to the solvent. Even more preferably, the boiling point of the solvents are relatively low to facilitate the removal, i.e., the evaporation, of the solvent from the substrate being treated. The following non-limiting examples reflect application of Applicants"" invention.